Method and device for heat treatment of body tissue

ABSTRACT

A device for heat treatment of prostate, comprising a treatment catheter with a fluid reservoir and heating means which is arranged within the treatment catheter and emits electromagnetic radiation for heating of the surrounding bodily tissue. The fluid reservoir constitutes an integrated part of the catheter for treatment and is positioned in the catheter so that, when inserted in a patient, it extends to cover the area heated by the heating means between the prostatic apex and bladder neck. The fluid reservoir also constitutes a closed chamber which is connectable via a channel passing through the catheter for treatment. A stop for the heat-absorbing means is embodied distal to said heating means and distal to said heat reservoir.

TECHNICAL FIELD OF THE INVENTION

The invention concerns a device for heat treatment of bodily tissue.

Heat treatment yields good treatment results with certain types ofdisease conditions involving unnatural growth of tissue. The tissue isheated to the extent that it dies. Examples of such disease conditionsare certain types of cancer and benign prostate hyperplasia, BPH. Duringtreatment certain portions of the tissue are heated so that tissue deathensues, while other portions of tissue must or should be protected. Thetemperature in the area of treatment should be at least 50° C. Durationof treatment is typically 1 hour but can be shorter. The diseaseconditions that are primarily indicated are those which occur in tissuesurrounding cavities in the body, for example the prostatic gland.

STATE OF THE ART

Different devices can be used in order to induce heating. Devices forheating by means of laser as well as with microwaves and radiofrequencies are common. A technique is known through U.S. Pat. No.5,257,977, according to which a catheter is provided with a reservoirfor fluid. The reservoir is flexible and is connected via channelsthrough the catheter with a heating device located outside the body. Afluid is heated in a heating device and circulated through the channelsand the reservoir. The rise of temperature in the reservoir brings aboutheating of the surrounding tissue.

Since the channels pass through tissue that should not be treated, theymust be heat insulated. According to U.S. Pat. No. 5,257,977 the heatinsulation is brought about by means of a space filled with gas thatsurrounds the channels. The function of the heat insulation is veryimportant, for which reason great care and considerable expense must bedevoted to this part of the treatment catheter.

A more highly developed catheter for treatment is shown and described inWO 97/02794, according to which a heating device is contained inside anexpandable reservoir. The heating device is provided with energy from anassembly outside of the body for heating of fluid inside the reservoir.Some of the disadvantages involving undesirable heating of certaintissue are avoided in this manner. The heating device is designedaccording to WO 97/02794 as a resistance wire or similar and heats thefluid through convection. The heat transferred from the fluid to thesurrounding tissue gives locally good results. A disadvantage is thatthe effect in the tissue at a farther distance from the reservoir isinsignificant.

Heat-treating with a treatment catheter that is equipped with amicrowave antenna is also known with the mentioned course of disease.Examples of such microwave treatment are known previously through U.S.Pat. Nos. 5,480,417 and 5,234,004. Characteristic for previously knownmicrowave treatment is that the prostate tissue is heated withmicrowaves. The intention is to heat parts of the prostate gland so thatthe tissue coagulates, i.e. dies. The element that emits the microwaveradiation consists of a coaxial cable With an antenna at its end that isincluded in a catheter for treatment. Cooling fluid circulates throughthe catheter. The intention with the cooling is to protect the prostaticurethra, that is to say the part of the urethra that runs through theprostate gland from being affected and damaged by the heat that isgenerated by the microwaves. Another reason for cooling the catheter isto transport away waste heat in the coaxial cable.

It has long been viewed as important to protect the part of urethra thatpasses through the prostate—the prostatic urethra—during microwavetreatment of benign prostate enlargement. This protection of theprostatic urethra hinders the treatment from being really effective,however, since parts of the obstructing tissue closest to the urethraare not heated but remain unaffected because of the cooling. Theclinical result of heat treatment is dependent on the amount of tissuethat coagulates. The degree of coagulation depends in turn ontemperature in combination with the length of treatment. The temperaturein turn depends on the input of energy and the carrying away of heat bythe blood flow. If cooling of the prostatic urethra is done for thepurpose of protecting it from being destroyed, the loss of heat energyfrom the area of treatment is increased, which is counterproductive andseverely diminishes the effectiveness of the treatment.

There are also designs with completely uncooled treatment catheters(U.S. Pat. No. 4,967,765). In such embodiments the microwave energymust, however, be limited so that the urethra and penis are not heateddue to cable losses in the coaxial cable that conducts the microwaves tothe antenna. Because of this restriction, completely uncooled cathetersare not preferred, since the microwave power that can then be used (max30 Watt) is so low that one cannot achieve the high tissue temperaturethat is needed in order for the coagulation of tissue to occur to thedesired extent.

THE INVENTION IN SUMMARY

A purpose of the invention is to increase the effectiveness of treatmentwith a treatment catheter of previously known technology. The highertreatment effectiveness means shorter treatment times. Alternatively,less microwave power can be used, which increases safety for thepatient.

The effectiveness of treatment is increased in that a treatment catheterdesigned for microwave treatment of the prostate contains a fluidreservoir filled with non-circulating fluid that surrounds the microwaveantenna between the prostatic apex and the bladder neck and thusprevents the prostatic urethra from being cooled during treatment Thefluid reservoir is heated partly by losses in the antenna device itselfthat are converted to Joule heat and partly by direct absorption ofmicrowave energy in the fluid itself. The absence of cooling of theprostatic urethra means that less microwave energy can be used toachieve the desired intra-prostatic temperature or alternatively thatthe treatment time can be shortened. Both possibilities are advantageousfor the patient in that they increase safety for the patient anddiminish the risk of damage caused by the treatment as a result of hightotal power output.

Further advantages and special features of the invention emerge from thefollowing description, drawings, and dependent patent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with the aid ofexamples of embodiments with reference to the attached drawings onwhich:

FIG. 1 is a principal cross-sectional view in the longitudinal directionof an embodiment of a treatment catheter according to the invention.

FIG. 2 is a transverse sectional view of the treatment catheter fromline II-II in FIG. 1,

FIG. 3 is a transverse view of the treatment catheter from line III-IIIin FIG. 1,

FIG. 4 shows a schematic connection of a treatment catheter to externaldevices according to one embodiment of the invention.

THE INVENTION

In the embodiment of a treatment catheter 12 according to the inventionas shown in FIG. 1 a reservoir 11 isolated from the catheter cooling ispositioned in the part of the catheter that is surrounded by theprostate gland. The treatment catheter is in the first place intendedfor treatment of prostate tissue. Before treatment reservoir 11 isfilled via a channel 22 in the treatment catheter 12 with fluid 13, forexample sterile water or cooking salt solution. Fluid 13 in thereservoir constitutes a dielectric that improves the adjustment betweenthe microwave antenna and the prostate tissue.

A heating device 10 is provided inside treatment catheter 12 for heatingtissue surrounding treatment catheter 12. Heating device 10 emitselectromagnetic radiation, preferably in the form of microwaves. Heatingdevice 10 suitably includes a microwave antenna. The energy emitted fromheating device 10 is absorbed to a small degree by the fluid inreservoir 11 but the overwhelming part of the energy is radiated outand. absorbed in the surrounding tissue. Energy is supplied via a feedcable 15 from an energy supply unit 14. (See FIG. 4.) In a preferredembodiment first heating device 10 includes an antenna that can bedesigned, for example, as a monopole antenna, dipole antenna, or a helixantenna. The antenna is covered by a protective sheath 40 up to itsradiating section in order to lessen radiation from other sections.

Treatment catheter 12 according to FIG. 1 is introduced through theurethra so that tip 16 extends into urinary bladder 21. A bladder orballoon 18 connected to the treatment catheter is expanded insideurinary bladder 21 and prevents unintended withdrawal of the treatmentcatheter during the process of treatment. The active part of thetreatment catheter is thus centrally located in the tissue that is to betreated, in this case in prostate 19 distal to bladder neck 21′. Thetreatment catheter 12 is flexible and pliable in order to be introducedflexibly through the urethra to the treatment position.

In the treatment catheter fluid channel 26 that ends in balloon 18 isalso present (see FIG. 2 and 3). Through it fluid can be supplied forexpansion of balloon 18 when the treatment catheter is brought into thedesired position for treatment. Fluid channel 26 is also used in orderto empty balloon 18 after treatment is completed and before thetreatment catheter is withdrawn from the urethra. A conventionalhypodermic needle or similar is suitably used for the filling andemptying of balloon 18.

Feed cable 15, through which energy is conducted to first heating device10, is heated as a result of losses. In order to avoid thermally induceddamage to tissue outside the area of treatment, for example on sphinctermuscle 29 that surrounds the urethra outside of the prostate or to thepenis, feed cable 15 is cooled. This is accomplished by providingcooling channels 27 in treatment catheter 12, preferably around feedcable 15. (See also FIG. 2 and FIG. 3.) Cooling channels 27 are embodiedaccording to the invention with a delimiter or stop 28, at which coolingfluid circulating in cooling channels 27 return. In this way cooling ofheating device 10 itself and of reservoir 11 is avoided, which in turnmeans that the energy that needs to be conducted from unit 14 can bediminished. With lower levels of energy, the risk of maltreatment anddamage to healthy tissue also diminishes.

Temperature sensors 23, 23′, and 23″ are arranged on carrier 24 in orderto be able to track the temperature development during heat treatment.Carrier 24 can be extended through a channel or tube 25, which runsthrough the treatment catheter. Carrier 24 or temperature sensor 23 issuitably embodied with, or as, a tip that can penetrate in part amembrane or wall in the treatment catheter and in part the bodilytissue. Tube 25 is embodied so that carrier 24 with temperature sensors23 is extended out of the treatment catheter at a suitable angle and canbe driven out to a suitably radial distance from the treatment catheter.

Heating of tissue thus occurs partly through heating of the fluidcontained in reservoir 11 that emits heat directly via heat conductionto adjacent tissue (i.e., the prostatic urethra) and partly throughelectromagnetic radiation. The total treatment area is thus larger thanwith conventional heating, where the prostatic urethra is cooled andthus not destroyed during treatment.

Fluid 13 in the reservoir is heated by interaction with microwaveantenna 10 to a temperature such that surrounding tissue, i.e., theprostatic urethra, is coagulated. Since the highest temperature isreached in the tissue closest to reservoir 11, the prostatic urethrawill to a large degree be affected and therewith be damaged and die.This part of the urethra is, however, regenerated relatively quickly. Aspecial temperature sensor 37 is suitably located in reservoir 11 forcontinuous measurement of the temperature of fluid 13 in reservoir 11.

A resulting heat profile, i.e. a curve that shows tissue temperatureradially outward from the centre of the treatment catheter, isaccordingly different from the profile that can be achieved withconventional technology employing a completely cooled catheter or a lackof cooling entirely.

When treatment is finished, the energy supply to heating device 10 isinterrupted and reservoir 11 can be emptied of fluid by suction viachannel 22. It is not suitable to remove the treatment catheter as longas the reservoir has a temperature such that damage may occur withpassage of the reservoir through the body. When catheter 12 isintroduced into the urethra with a tip into urine bladder 21, drainageof urine and any other fluid from the urine bladder can occur through adrainage channel provided in catheter 12. The drainage channel runsthrough the whole catheter 12 and ends with an opening 20 near the tipof catheter 12. With certain types of treatment it can be suitable toleave catheter 12 in place during a certain period of time after thetreatment. The function of the drainage channel during this time is alsoto drain the urine bladder.

As soon as urine passes again through the urethra in the prostate, thetreated and dead tissue will be eliminated with the urine. A remaininghollow space in the prostate after the tissue was removed assures thepassage of urine in the correct manner. The process of healing includingelimination of coagulated tissue can continue for some months.

FIG. 2 schematically shows an embodiment of a treatment catheter 12.Treatment catheter 12 is designed with a number of cavities and channelsextending along the treatment catheter. Feed cable 15 runs through acentral cavity 30, which is preferably well shielded. Cooling fluid istransported in separated cooling channels 27, preferably in acirculating system. In a first cooling channel 27 a tube 25 for carrier24 is arranged. In a similar manner fluid channel 26 for balloon 18 andchannel 22 for fluid reservoir 11 are arranged in other cooling channels27. A drainage channel, which ends in opening 20 in the treatmentcatheter, can be arranged in a similar way in a cooling channel.

The cross section view in FIG. 3 shows an example of how reservoir 11can be embodied. Essentially the whole internal volume of treatmentcatheter 12 is occupied by reservoir 11. Partition walls are indicatedand can be used, for example, in order to control feed cable 15 andfluid channel 26 for balloon 18. Reservoir 11 can alternatively consistof connected channel elements that constitute a continuation of coolingchannels 27 after stop 28.

The block diagram in FIG. 4 schematically shows the various functionblocks that can be included in a treatment assembly with a treatmentcatheter according to the invention. As indicated above, energy issupplied to heating device 10 from energy supply unit 14. A centralcontrol unit 32 is operatively connected with energy supply unit 14 anda display unit 33 and with a pumping and cooling device 34 and a fluidsupply device 35. Control unit 32 is additionally operatively connectedto an input device, for example, in form of a keyboard 36. Control unit32, keyboard 36, and display unit 33 can also be included in aconventional computer with a monitor and keyboard.

Control unit 32 is operatively connected to temperature sensors 23 and37 and can control energy supply unit 14 dependent on the currenttemperature in the area of treatment so that suitable power is suppliedto heating device 10. In this manner it is possible to increase thetemperature considerably with good safety in fluid reservoir 11 and thusin surrounding tissue so that tissue death occurs in the desired way.Data on temperature from temperature sensors 23 and 37 can also be showncontinuously on display unit 33.

Pumping and cooling device 34 is connected to cooling channels 27 andpumps suitable cooling fluid through cooling channels 27 in orderprimarily to cool feed cable 15 while it is being extended forward toheating device 10. Fluid supply device 35 is used when fluid reservoir11 is to be filled and emptied. Control unit 32 can monitor the pumpingand filling.

A preferred embodiment according to the invention also includes apressure meter 17 that is operatively connected to reservoir 11 in orderto monitor the pressure in the reservoir. Pressure meter 17 is alsooperatively connected to central control unit 32 so that the pressure influid reservoir 11 will affect the process of treatment. The pressure ischanged depending on how the treatment proceeds. For reasons of safetythe treatment should be interrupted if the pressure in fluid reservoir11 falls abruptly, for example as a result of the failure of a partitionin reservoir 11. In a corresponding way, treatment should be interruptedif the temperature in reservoir 11 becomes so high that the fluid in itboils.

Feed cable 15 can be embodied in the form of a coaxial cable with aprotective sheath and an inner conductor. The sheath also constitutes anouter conductor. The inner conductor acts as an antenna beyond the endof the sheath.

What is claimed is:
 1. A catheter for insertion into a urethra toperform heat treatment of a prostate which surrounds a prostatic urethraof the urethra in a human being, comprising: an antenna located at aposition within the catheter adjacent to the prostatic urethra and theprostate upon insertion of the catheter into the urethra to a treatmentposition at which the treatment is performed, the antenna emittingelectromagnetic radiation to heat at least a portion of the prostatesurrounding a portion of the prostatic urethra; a fluid reservoir withinthe catheter surrounding the antenna and located to extend along aportion of the prostatic urethra upon positioning the catheter in thetreatment position, the fluid reservoir for containing fluid surroundingthe antenna to absorb heat from the antenna and from some of the emittedelectromagnetic radiation and to apply that absorbed heat through thecatheter to the prostatic urethra and prostate tissue surrounding thereservoir; a feed cable extending along the catheter from a position atan exterior of the urethra, the feed cable operatively connected to theantenna to conduct energy to the antenna, the feed cable emitting heatas a result of conducting energy to the antenna; a cooling channelwithin the catheter and extending along the feed cable, the coolingchannel for conducting cooling fluid to remove the heat emitted from thefeed cable and to protect the urethra and the tissue surrounding thefeed cable from the heat emitted from the feed cable; a delimiterseparating the fluid reservoir from the cooling channel; and a channelextending through the delimiter for conducting fluid into and out of thefluid reservoir.
 2. A catheter as defined in claim 1, wherein: thecooling channel and the delimiter permit the cooling fluid to circulatewithin the cooling channel; and the delimiter and the fluid reservoirprevent circulation of the fluid in the fluid reservoir.
 3. A catheteras defined in claim 2, wherein: the delimiter prevents fluid in thereservoir from circulating with the fluid in the cooling channel.
 4. Acatheter as defined in claim 1, wherein: the delimiter prevents thecooling fluid in circulation within the cooling channel from cooling thefluid in the reservoir.
 5. A catheter as defined in claim 1, wherein:the delimiter confines the heat in the fluid in the reservoir forapplication through the catheter to the prostatic urethra and theportion of the prostate, and confines the cooling fluid to remove theheat from the feed cable without transferring sufficient heat from thefeed cable to damage the urethra and the tissue surrounding the coolingchannel.
 6. A catheter as defined in claim 1, wherein: the channelextending through the delimiter further extends along the catheter to aposition exterior of the urethra.
 7. A catheter as defined in claim 1,wherein: the reservoir is formed in part by a continuation of thecooling channel extending distally beyond the delimiter.
 8. A catheteras defined in claim 1, for use relative to a sphincter muscle whichsurrounds the urethra at a position proximal of the prostatic urethra,wherein; the delimiter is located at a position adjacent to thesphincter muscle upon positioning the catheter in the treatmentposition.
 9. A catheter as defined in claim 1, for use relative to aprostatic apex which surrounds a proximal end of the prostatic urethra,wherein: the delimiter is located adjacent to the prostatic apex uponpositioning the catheter in the treatment position.
 10. A catheter asdefined in claim 1, for use relative to a bladder neck which surroundsthe urethra where the urethra extends from a bladder of the human beingand for use relative to a prostatic apex which surrounds a proximal endof the prostatic urethra, wherein: the fluid reservoir has a lengthwhich extends substantially between the bladder neck and the prostaticapex upon positioning the catheter in the treatment position.
 11. Acatheter as defined in claim 1, further comprising in combination: afluid supply device connected to the channel at a position exterior ofthe urethra for supplying fluid through the channel to the fluidreservoir.
 12. A catheter as defined in claim 1, further comprising: aheat sensor positioned to sense temperature of fluid within the fluidreservoir.
 13. A catheter as defined in claim 12, further comprising incombination: an energy supply unit connected to the feed cable at aposition exterior of the urethra to supply the energy conducted by thefeed cable to the antenna; and a central control unit connected to theenergy supply unit to control the amount of the energy conducted fromthe energy supply unit to the feed cable; and wherein: the heat sensoris operatively connected to the central control unit; and the centralcontrol unit controls the amount of energy conducted from the energysupply unit through the feed cable to the antenna in response to thetemperature sensed by the heat sensor.
 14. A catheter as defined inclaim 1, further comprising: a pressure meter positioned to monitorpressure of fluid within the fluid reservoir.
 15. A catheter as definedin claim 14, further comprising in combination: an energy supply unitconnected to the feed cable at a position exterior of the urethra tosupply the energy conducted by the feed cable to the antenna; and acentral control unit connected to the energy supply unit to control theamount of the energy conducted from the energy supply unit to the feedcable; and wherein: the pressure meter is operatively connected to thecentral control unit; and the central control unit controls the amountof energy conducted by the energy supply unit through the feed cable tothe antenna in response to the fluid pressure monitored by the pressuremeter.
 16. A catheter as defined in claim 1, further comprising: acarrier moveably positioned within the catheter, the carrier having atip which penetrates into the prostate at a radial distance relative tothe catheter upon extension of the carrier when the catheter ispositioned in the treatment position; and a temperature sensor connectedto the carrier at a position which measure the temperature of theprostate at the radial distance from the catheter.
 17. A catheter asdefined in claim 16, further comprising in combination: an energy supplyunit connected to the feed cable at a position exterior of the urethrato supply the energy conducted by the feed cable to the antenna; and acentral control unit connected to the energy supply unit to control theamount of the energy conducted from the energy supply unit to the feedcable; a display connected to the central control unit to displayinformation; and wherein: the temperature sensor is operativelyconnected to the central control unit; and the central control unitdisplays information obtained from the temperature sensor relating tothe temperature of the prostate at the radial distance.
 18. A catheteras defined in claim 17, wherein: the central control unit controls theamount of energy conducted from the energy supply unit through the feedcable to the antenna in response to the temperature sensed by thetemperature sensor.
 19. A catheter as defined in claim 16, furthercomprising: a plurality of the temperature sensors connected to thecarrier at positions which measure the temperature of the prostate at aplurality of different radial distances from the catheter.
 20. Acatheter as defined in claim 19, further comprising in combination: anenergy supply unit connected to the feed cable at a position exterior ofthe urethra to supply the energy conducted by the feed cable to theantenna; and a central control unit connected to the energy supply unitto control the amount of the energy conducted from the energy supplyunit to the feed cable; a display connected to the central control unitto display information; and wherein: the temperature sensors areoperatively connected to the central control unit; and the centralcontrol unit displays information obtained from the temperature sensorsrelating to the temperatures of the prostate at the different radialdistances.
 21. A catheter as defined in claim 20, wherein: the centralcontrol unit controls the amount of energy conducted from the energysupply unit through the feed cable to the antenna in response to thetemperatures sensed by the temperature sensors.
 22. A method for heattreating a prostate which surrounds a prostatic urethra of a urethra ina human being by using a catheter having an electromagnetic radiationemitting antenna and a feed cable connected to the antenna and extendingalong the catheter, comprising: inserting the catheter into the urethrato a treatment position at which the antenna is adjacent to theprostatic urethra and the prostate; energizing the antenna to emitelectromagnetic radiation to heat at least a portion of the prostatesurrounding a portion of the prostatic urethra; surrounding the antennawith fluid in a reservoir to absorb heat from the antenna and from someof the emitted electromagnetic radiation and to apply that absorbed heatthrough the catheter to a portion of the prostatic urethra and a portionof the prostate surrounding the prostatic urethra; conducting energy tothe antenna through the feed cable; emitting heat from the feed cable asa result of conducting the energy through the feed cable; circulatingcooling fluid within the catheter along the feed cable to remove heatemitted from the feed cable to protect the urethra and the tissuesurrounding the feed cable from the heat emitted by the feed cable; andseparating the cooling fluid circulating along the feed cable from thefluid surrounding the antenna.
 23. A method as defined in claim 22,further comprising: confining circulation of the cooling fluid along thefeed cable.
 24. A method as defined in claim 22, further comprising:conducting fluid into and out of the reservoir.
 25. A method as definedin claim 22, further comprising: preventing cooling-fluid surroundingthe feed cable from circulating in the reservoir.
 26. A method asdefined in claim 22, further comprising: preventing fluid in thereservoir from circulating with cooling fluid surrounding the feedcable.
 27. A method as defined in claim 22, further comprising:transferring sufficient heat from the feed cable to the cooling fluid toprevent damage the urethra and the tissue surrounding the coolingchannel.
 28. A method as defined in claim 22, for use relative to asphincter muscle which surrounds the urethra at a position proximal ofthe prostatic urethra, further comprising: separating the cooling fluidcirculating along the feed cable from the fluid surrounding the antennaat a position adjacent to the sphincter muscle.
 29. A method as definedin claim 22, for use relative to a prostatic apex which surrounds aproximal end of the prostatic urethra, further comprising: separatingthe cooling fluid circulating along the feed cable from the fluidsurrounding the antenna at a position adjacent to the prostatic apex.30. A method as defined in claim 22, for use relative to a bladder neckwhich surrounds the urethra where the urethra opens from a bladder ofthe human being and for use relative to a prostatic apex which surroundsa proximal end of the prostate urethra, further comprising: extendingthe reservoir substantially between the bladder neck and the prostaticapex.
 31. A method as defined in claim 22, further comprising: sensing atemperature of fluid within the reservoir.
 32. A method as defined inclaim 31, further comprising: controlling an amount of the energyconducted through the feed cable relative to the sensed temperature offluid within the reservoir.
 33. A method as defined in claim 22, furthercomprising: monitoring a pressure of fluid within the reservoir.
 34. Amethod as defined in claim 33, further comprising: controlling an amountof energy conducted through the feed cable relative to the pressure tothe fluid within the reservoir.
 35. A method as defined in claim 22,further comprising: penetrating a temperature sensor into the prostatefrom the catheter at a radial distance relative to the catheter; andmeasuring the temperature of the prostate at the radial distance fromthe catheter.
 36. A method as defined in claim 35, further comprising:displaying temperature Information obtained at the temperature sensor.37. A method as defined in claim 36, further comprising: controlling anamount of energy conducted through the feed cable in relation to thetemperature of the prostate sensed by the temperature sensor.
 38. Amethod as defined in claim 22, further comprising: penetrating aplurality of the temperature sensors into the prostate from the catheterat a plurality of different radial distances from the catheter.
 39. Amethod as defined in claim 38, further comprising: displayingtemperature information obtained from the plurality of temperaturesensors.
 40. A method as defined in claim 39, further comprising:controlling an amount of energy conducted through the feed cable inrelation to the temperature of the prostate sensed by the plurality oftemperature sensors.